Jinzaemon is not black (that's who you meant right?):

https://sekiroshadowsdietwice.wiki.fextralife.com/Jinzaemon+...

From the wiki though: > (Japanese Default Language version) He has a Westernized Japanese accent, it may be a tribute to Yasuke (African Samurai) in 1579.

Erm, ok, that's a weird reach the wiki is making. You can see closeups of his face right beneath that sentence.